1. Field of the Invention
The present invention relates to a vibration correction apparatus.
2. Related Background Art
An image of a subject picked up with a compact video camera vibrates by hand vibrations or other vibrations, and this image becomes very unwatchable. Recently, video cameras using a high magnification factor lens have been used widely, so that a vibration becomes conspicuous particularly when the lens is located in a telephoto side.
A number of video cameras having a vibration correction function of correcting such a vibration have been proposed and manufactured.
For example, a video camera having a vibration correction function (hereinafter simply called a video camera) optically corrects a vibration of an image. To this end, the video camera is provided with an angular velocity sensor for detecting vibrations such as hand vibrations and a variable angle prism (VAP) for correcting the image in accordance with the detected vibration.
In such a video camera, a filtering process is performed in which after the d.c. components of a signal detected with an angular velocity sensor are removed and the signal is amplified, the low frequency components thereof are cut. With this filtering process, a target value of an apex angle of VAP is obtained, and in accordance with the target value, the apex angle of VAP is changed to optically correct a vibration of an image.
There is a video camera whose lens unit can be replaced, the lens unit being constituted of an angular velocity sensor and VAP. This video camera can broaden a photographing range.
However, a sensitivity of detecting a vibration with the angular velocity becomes lower in the lower frequency band. The phase in the low frequency band becomes not ideal because of signal processing or the like. Therefore, the conventional video camera gives a user a poor performance of vibration correction in the low frequency band. This problem becomes more conspicuous if the video camera uses a high magnification factor lens.
In view of this, it has been proposed to improve the performance of vibration correction in the low frequency band by using both a motion between fields of picked-up images and a motion detected with an angular velocity sensor. However, since the sampling period of detecting an image motion is slow and the target value of the apex angle of VAP is changed (renewed) at this period, an image with a low resolution is formed, or since the field period is slow, VAP may vibrate or produce sounds.
In order to solve these problems, the present applicant has filed a method of driving a correction system (VAP) at a shorter period than the motion detection period (JP-A-08-304672) to allow a smooth correction operation.
However, if an interpolator is used for raising an renewing period of the target value of an apex angle of VAP, the interpolator suitable for each television system is required because the sampling period of detecting an image motion changes with the television system. Similarly, in the case of a video camera having a detachable lens unit, if an interpolator is provided in the lens unit, the lens unit matching the television system is required.
With such a configuration, the apparatus structure becomes complicated, and the replacement of the lens unit becomes essential, resulting in a very cumbersome work.
With the further studies after the above-cited application was filed, it has been found that a precision of interpolation calculation is effected by an operation of a correction system so that the calculation precision is required to be improved or other measures are required to be performed.
It has also been found that there is some room in studying the optimization of the characteristics of a panning/tilting operation.
The present invention has been made in order to solve the above problems. It is a first object of the present invention to allow a vibration correction operation to be always good and highly precise, irrespective of what type of an image pickup system is utilized.
In order to achieve the first object of the invention, a preferred embodiment discloses an image pickup apparatus comprising: image pickup means for picking up an image of a subject and generating an image signal; motion detecting means for detecting a motion of the image from the image signal generated by the image pickup means; generating means for generating a correction target value in accordance with a detection result by the motion detecting means; correcting means for correcting a motion of the image in accordance with the correction target value generated by the generating means; and control means for controlling to make variable a sampling period of the correction target value generated by the generating means, in accordance with an image pickup system or a television system.
It is a second object of the present invention to improve the characteristics of a correction system by shortening a correction period shorter than a vibration detection period, and to always allow a high precision correction system control irrespective of any operation state of the correction system.
In order to achieve the second object of the invention, a preferred embodiment discloses an image pickup apparatus comprising: motion vector detecting means for detecting a motion vector signal at a predetermined sampling period; first signal processing means for calculating a correction target value in accordance with the motion vector signal detected by the motion vector detecting means; second signal processing means for storing the correction target value calculated by the first signal processing means and outputting a correction target value obtained through time-division of the stored correction target value until the next sampling time, in accordance with the motion vector signal detected by the motion vector detecting means; and optical vibration correcting means for correcting a vibration of an image in accordance with the correction target value time-divided by the second signal processing means.
It is a third object of the present invention to optimize the control of the correction system during the panning/tilting and camera fixed operations.
In order to achieve the third object of the invention, a preferred embodiment discloses an image pickup apparatus comprising: motion detecting means for detecting a motion vector of an image on an image pickup plane; vibration detecting means for detecting a vibration amount of the image pickup apparatus; first signal processing means for calculating a first correction target value in accordance with a vibration amount signal detected by the vibration detecting means; optical vibration correcting means for correcting a vibration of an image; and second signal processing means for calculating a second correction target value by weighing the motion vector detected by the motion detecting means, in accordance with both or one of output signals from the vibration detecting means and the first signal processing circuit.
Another object of the present invention to improve the precision of a correction system by shortening a correction period shorter than a vibration detection period, and to allow a necessary interpolation process or the like to be performed smoothly and at high precision.
The other objects and features of the invention will become more apparent from the following detailed description of the embodiment when read in conjunction with the accompanying drawings.